square tubing.

[therail]

Does square tubing belong any where on a chassis? I guess what i mean is, is round that much superior? My dad works for an oil company and is great friends with the manager of their rig fab yard and I cant get high grade square tubing all day long for free as long as I need a reasonable amount. So should i use it for small things?

By the way, this isnt for my truck. Its going to be used on my go-kart, lol. Yes it seems childish, but I'm building a cage for it and dont wanna get hurt.

[zjohnson]

Square tubing has stress concentrations built into it. It can be used, but the strength to weight ratio of round tube is way better.
good luck

[ffjerm]

Square or rectangular tubing is often used as the bottom rails on land-speed cars, as well as most street rods. for your purpose, square tube would work fine on the bottom rail, but a roll cage made of square tube would look pretty strange. making round corners out of square tube requires numerous pie cuts and takes alot of extra time. they do make dies for bending square tube, but i never used one. personaly, i'd use the free square tube for the bottom rails, engine mounts, seat rails etc, then spend the cash for round tubing to construct the roll cage. i can't imagine the added cost would be very much, and your go-cart would look alot better.

[ntsqd]

Square or rectangular tube has a place where you know the direction of all of the loadings and can orient the tube so that it is in it's strongest orientation relative to those loads.
If you don't know where the loads are, or their direction, you are better off with round tube as it is the same strength in any direction.

[67BAJA]

Find a guy that get's round tube for free all day long but needs square tube. Best friends for life

[Junior]

Protrucks have rectangular tubing used for frame rails I believe.

Jr

[J_Lothringer]

Porter race cars love the stuff................

[gwm]

Porter race cars love the stuff................

I'm trying to recall Scott McMillin's (Jeffries) Porter. I know they used it on suspension pieces, but did Porter use it on the chassis?

[therail]

well guys thanks for the input. i guess ill just skip on the free stuff, round look better anyways. :-)

[Stephen]

I'm sometimes surprised you don't see more square tube on race vehicles, the strength of the vertical leg is huge compared to round, as long as you need that leg oriented one direction. One problem is availability in strong alloys, then there's corner radius changes in different sizes, etc. Still it's good stuff if it's loaded the strong way.

[Scott_F]

The new Alpha Class 1 car has large square section beams on the bottom of the chassis. They are around 4-5" square. I think using square or rectangular tubing on the bottom of the chassis is ok, but I would use it sparingly elsewhere.

http://www.race-dezert.com/forum/showthread.php?t=14318

[matt09]

im building a roll cage for my truck. i wanted to use square chromolly tubing for the main hoops because i thought it might be stronger. what do you guys think?

[Scott_F]

No one does that because it is not a good idea. Square tubing is stronger than round in two directions, but weaker in other directions. When a vehicle is rolled hard, loads can come from all directions. Round tubing is equally strong in all directions.

[matt09]

i agree but, what if the square tubing is the same wall thickness of the round tubing and its width is the same as the diameter (i.e. 2" x .12" round tubing vs. 2" x 2" x .12" square tubing) then would the square tubing be a better choice?

[Josh_K]

I think you guys have missed 2 basic points.
1. You cant roll the a square tube in a die to make a bend that is off of the planes of the flat sides of it and 2 Every square tube I have ever seen bent pushes in the inner flang of the bend and pulls the outer flang of the bend inward thus disforming the tubing if you dont use a true mandral bender. This is far less of a issue with round tubing.

[matt09]

what if you weren't going to bend it but instead cut two lengths of square tubing at equal angles and then weld them together to form the angle. or even cut a "V" shape in a piece of square tubing and then heating it up and bending the side not cut and welding it together.

[Josh_K]

what if you weren't going to bend it but instead cut two lengths of square tubing at equal angles and then weld them together to form the angle. or even cut a "V" shape in a piece of square tubing and then heating it up and bending the side not cut and welding it together.


If you did it correct and cut at a 45 and plated and gusseted the joint, I think it would be stronger that a round of the same dia and material. Just dont use electric welded tubing.

Here is a simpel question, What weights more? a foot of round or square 2" x .120" wall.

[matt09]

im sorry, but what did you mean when you said not to use electric welded tubing. thats basically the only square tubing avalible.

[FABRICATOR]

Weight of 10' x .120 x 2" round steel tube: 24.1 pounds.
Weight of 10' x .120 x 2" square steel tube:29.5 pounds.

Square tube has a high flex/stress ratio (rigid). Piecing it together, notching it, gusseting it, only makes the condition worse. A square tube roll structure with rigid stress risers could experience catastrophic failure if forced to bend. Not only would this compromise protection, but a displaced tube could create additional hazards. On the other hand, bent square or rectangular tube roll structures are quite common on low speed vehicles and heavy equipment.

[matt09]

Square tube has a high flex/stress ratio (rigid). Piecing it together, notching it, gusseting it, only makes the condition worse.
how can gusseting make square tubing worse and whats wrong with a rigid roll cage?

[handmethemic]

Too rigid, and a rollover will break your collarbones. The cage will break apart before it bends if it's too rigid. You want it to bend A LITTLE, reduces the forces of crashing. It's physics. You want the deceleration of the object (here the rolling ball of death* that you're going to be strapped into) to be spread out over a longer distance to keep the forces too high. F= M x A. Same reason passenger cars have crumple zones.

*not referring to your vehicle... any vehicle that anyone rolls is potentially deadly

[Josh_K]

[QUOTE On the other hand, bent square or rectangular tube roll structures are quite common on low speed vehicles and heavy equipment.[/QUOTE]

The worlds fasted commercail class 8 truck (big trucks) has a cage made from 2"x4"x.25 wall tube. I think its Bonnaville speed was just over 190 mph.

It had a 16v 91 2 cycle detroit in it. On top of the each blower it had 1.5" fuel line that would pure raw fuel into the engine at above 2500 rpm. With 2 blower and 4 turbos they guessed that it make 3500 hp at 3500 rpm with about 5 or 6k lbs of torque.

[handmethemic]

But that's huge dimensions for tubing that would be completely ridiculous for anything but framerails on a desert runner. That large of square tubing is surely safe for damn near any application but to make a light efficient desert car? Not a chance.

[Josh_K]

But that's huge dimensions for tubing that would be completely ridiculous for anything but framerails on a desert runner. That large of square tubing is surely safe for damn near any application but to make a light efficient desert car? Not a chance.

All true, but its not that big if your in a truck that weights 15+k and you put it on its lid at 190 mph.

Oh ya it would lay down more black smoke than a challanger locomotive .